Conradson carbon ("Concarbon") number ("CCN") is a measure of the characteristic tendency or propensity of a petroleum feedstream to form coke during processing. Feedstreams having a lower Concarbon number are more economically desirable as refinery feeds than feedstreams having a higher concarbon number. For example, U.S. Pat. No. 5,514,252 discloses reductive electrochemical treatment of refinery streams which occurs at specified cathodic voltage to decrease Conradson carbon number. High hydrogen overpotential cathodes such as lead and mercury are disclosed. There is a continuing need for additional processes for reducing the Concarbon number of feedstreams. Applicant's invention addresses this need.